Earth smaller than previously believed

 

Although the discrepancy is only millimetres in size, the discovery may correlate with the observed rise in sea levels.

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Geodesists from the University of Bonn have re-measured the size of the Earth in a long-lasting international cooperation project. Our planet is now thought to be a few millimetres smaller than first assumed.

The significance of this finding is that scientists will be able to better demonstrate a climate related rise in sea level.

The system of measurement used by the Bonn Geodesists is invisible - it consists of radiowaves that are transmitted into space from tiny sources, so-called Quasars.

A network of more than 70 radio telescopes worldwide receives these waves, but because the ‘gaging’ stations are so far apart from each other, the radio signals are received with a slight time-lag.

"From this difference we can measure the distance between the radio telescopes—and to the preciseness of two millimetres per 1,000 kilometres,” explained Dr. Axel Nothnagel, the research group leader for the Geodesy Institute of the University of Bonn.

Very Long Baseline Interferometry

The procedure is called VLBI, which stands for "Very Long Baseline Interferometry".

The technique can be used, for example, to demonstrate that Europe and North America are distancing from each other at a rate of about 18 millimetres annually.

The distance of the gaging stations from each other allows the size of the Earth or the exact location of the centre of the Earth to be determined.

"We have analyzed the measurements and calculations from 34 partners in 17 countries," explained Nothnagel.

"A combination of GPS and satellite laser measurements will enable the availability of the coordinates from almost 400 points on the surface of the Earth with unparalleled exactness."

The results are the basis for a new coordinate system for the planet.

The results have now appeared in the renowned Journal of Geodesy.

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